1. Field of the Invention
The invention relates to a process for the production of sulphur from at least one sour gas containing H.sub.2 S and a gaseous or liquid fuel effluent. It further relates to a thermal reactor which can be employed in implementing the said process.
2. Background Art
The preparation of sulphur from a sour gas containing hydrogen sulphide by the Claus process consists in a controlled oxidation of the hydrogen sulphide by the oxygen of a gas containing free oxygen, the said oxidation being prolonged in contact with a catalyst. The sour gas containing hydrogen sulphide is brought into a thermal reaction stage in which approximately a third of the hydrogen sulphide is converted into SO.sub.2 by controlled combustion in the presence of a gas containing free oxygen and a certain quantity of sulphur is formed. The gaseous reaction mixture/originating from the thermal reaction stage is then subjected to indirect cooling making it possible to recover the heat energy which it contains by producing steam, and the said cooled mixture is directed towards a condensation stage in which the sulphur present in the gaseous mixture is separated by condensation. To drive further the sulphur production, which at this stage is still very incomplete, the gaseous mixture originating from the condensation stage is reheated and then brought to a catalytic reaction stage containing a suitable catalyst in contact with which the SO.sub.2 and H.sub.2 S present in the said mixture react with each other to form a new quantity of sulphur. The catalytic conversion generally requires two or three catalytic zones, each of which is preceded by a heater for the gas mixture to be treated and followed by a condenser in which the sulphur formed separates out. The residual gases originating from the final catalytic zone, which still contain small quantities of sulphur compounds such as H.sub.2 S, SO.sub.2, sulphur vapour and/or vesicular sulphur, COS and CS.sub.2 optionally flow into a purification stage, which still retains a high proportion of the sulphur compounds present in the said residual gases, before being directed towards an incineration stage to be then discharged into the atmosphere.
In some cases it may be necessary in the thermal reaction stage to perform the combustion of a gaseous fuel effluent so that it accompanies the controlled oxidation of H.sub.2 S. Thus, when a fuel effluent is available which consists of a residual gas or of a liquid containing sulphur compounds, especially organic sulphur compounds and possibly ammonia or ammonia-forming compounds, the abovementioned combustion makes it possible to destroy the sulphur and nitrogen compounds in the fuel effluent and to form SO.sub.2 from the said sulphur compounds, this SO.sub.2 being added to the SO.sub.2 produced by the controlled oxidation of H.sub.2 S in the sour gas. Another example of a combustion of the abovementioned kind is encountered in the treatment of an H.sub.2 S-lean sour gas in the thermal reaction stage, the fuel effluents then consisting of a heating gas whose combustion allows the temperature in the thermal reaction stage to be raised to the required value, which cannot be obtained merely by the controlled oxidation of the H.sub.2 S-lean sour gas.
The known processes for simultaneously producing, on the one hand, the combustion of a gaseous or liquid fuel effluent and, on the other hand, the controlled oxidation of H.sub.2 S in a sour gas while operating in the thermal reaction stage of a Claus sulphur production plant do not make it possible to carry out this treatment over a wide range of flow rates and compositions while completely satisfying the requirements linked with obtaining, at the exit of the thermal reaction stage, a reaction gas stream of the quality needed for a subsequent treatment in the catalytic stage of the Claus plant, that is to say with obtaining a gas stream containing H.sub.2 S, SO.sub.2 and sulphur vapour and virtually free from NH.sub.3, SO.sub.3, hydrocarbon and nitrogen oxide impurities.
The subject of the invention is a process which makes it possible simultaneously to carry out the total combustion of a gaseous or liquid effluent and the controlled oxidation of the H.sub.2 S in at least one sour gas in the thermal reaction stage of a Claus sulphur production process, under conditions such as to produce, at the exit of the said thermal reaction stage, a reaction gas stream containing H.sub.2 S, SO.sub.2 and sulphur vapour and containing virtually none of the impurities referred to above, over an extensive range of flow rates and compositions.